Mentzelia affinis
Mentzelia leucophylla
yellow comet
Ash Meadows blazingstar
multiple, erect, straight;
branches distal or along entire stem, distal longest or all ± equal, antrorse, straight; hairy.
blade 15–61 × 8–28.5 mm, widest intersinus distance 6–23.8 mm;
proximal obovate, ovate, or broadly elliptic, margins usually dentate to serrate, rarely entire, teeth (0–)6–20, slightly antrorse or perpendicular to leaf axis, 0.4–4 mm;
distal deltate to cordate, base clasping, margins usually dentate, rarely entire, teeth (0–)6–12, perpendicular to leaf axis, 0.5–2 mm;
abaxial surface with complex grappling-hook and needlelike trichomes, adaxial surface with needlelike trichomes, both surfaces whitish, densely hairy.
persisting;
petiole present or absent;
blade linear-lanceolate to linear, margins usually deeply to moderately lobed, sinuses extending 1/4+ to midvein, rarely entire.
petiole absent;
blade ovate-lanceolate to lanceolate, to 17 cm, margins usually dentate or entire, rarely deeply lobed.
green, ovate to lanceolate, 2.7–6.6 × 0.9–2.1 mm, width 1/5–1/3 length, not concealing capsule, margins 3-lobed or entire.
margins entire.
sepals 1–7 mm;
petals yellow to orange proximally, yellow distally, 4–12 mm, apex acute;
stamens 20+, 3–6.5 mm, filaments monomorphic, filiform, unlobed;
styles 3–6.5 mm.
petals golden yellow, 9.2–13.2 × 2.8–5 mm, apex rounded, glabrous abaxially;
stamens golden yellow, 5 outermost petaloid, filaments narrowly spatulate, slightly clawed, 6–10.6 × 1.3–2.6 mm, with anthers, second whorl with anthers;
anthers twisted or straight after dehiscence, epidermis smooth;
styles 6–8.1 mm.
narrowly cylindric, 7–32 × 1–3 mm, axillary curved to 90° at maturity, often prominently longitudinally ribbed.
cup-shaped, 5–9.5 × 6–8.6 mm, base rounded, not longitudinally ridged.
10–20, in 1 row distal to mid fruit, tan, dark-mottled or not, triangular prisms, surface ±smooth under 10x magnification; recurved flap over hilum absent;
seed coat cell outer periclinal wall flat.
coat anticlinal cell walls straight, papillae 11–13 per cell.
= 18.
= 36.
Mentzelia affinis
Mentzelia leucophylla
Herbarium specimens of Mentzelia affinis are often difficult to distinguish from those of M. dispersa despite distinct evolutionary histories (J. M. Brokaw and L. Hufford 2010). Several characters, including flower size, leaf margins, and capsule surfaces, differ substantially between these species, but habitat is the most dependable diagnostic character. Verified populations of M. affinis have not been found above 1200 meters in desert habitats, and grassland populations are usually restricted to much lower elevations. Sympatric populations of M. affinis and M. dispersa have not been found, and, in areas of range overlap in southern California, M. dispersa has not been found below 1200 meters or in desert vegetation.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
Mentzelia leucophylla is known only from the Ash Meadows of Nye County (N. H. Holmgren et al. 2005). It is morphologically similar to M. oreophila, which occurs in Nye County and elsewhere, but the two taxa are not known to co-occur. Trichome density, despite being difficult to quantify, provides perhaps the easiest method to differentiate the two taxa, with the densely hairy leaves of M. leucophylla appearing whitish. In addition to characters provided in the key, M. leucophylla, which is up to seven decimeters tall, is often more robust than M. oreophila, which is no more than six decimeters tall.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
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